Conventionally, a system that detects, on the basis of an image obtained by a camera (in-vehicle camera) mounted on a vehicle such as a car, vehicles present around the vehicle and utilizes the detection result for driving support for a driver has been developed. As an example of such a system, for example, an inter-vehicle distance keeping system (ACC) that automatically keeps the inter-vehicle distance from a vehicle present around the own vehicle, or a collision avoiding system that warns the driver with an alarm or the like when there is a possibility of collision with a vehicle or the like present around the own vehicle and that reduces the damage to an occupant with automatic braking or the like when the situation reaches the point where collision becomes inevitable is known.
Particularly, in the case of using a stereo camera device including a plurality of cameras, visual information based on images captured by a camera and information about the distance to an object present in the images can be simultaneously obtained, and various objects (such as people, vehicles, three-dimensional objects, the road surface, road markings, and road signs) around the vehicle can be recognized in detail. This is considered to contribute to the improvement of safety in driving support.
While attempt to improve the precision of object detection techniques utilizing image processing that makes up the core of the inter-vehicle distance keeping system and the collision avoiding system has been continued, computation resource that can be utilized by an in-vehicle device is limited, and a quick response speed is also desired. Therefore, in this field, development of technology that meets mutually contradictory requirements such as improvement of detection precision, reduction of computation load, and improvement of response speed is desired.
To meet the desire like this, PTL 1 discloses a technique of measuring a precise distance to an object present in an image by improving the precision of distance in measuring the distance to the object.
An image processing apparatus disclosed in PTL 1 is an apparatus that extracts one-image object region including an image of an object from one of a pair of images obtained by performing image capturing by a pair of image capturing elements at the same time in the same direction, calculates, for each of plural image constituting parts constituting the one-image object region, a background degree that is a degree of certainty indicating whether the image constituting part is an object image constituting part or a background image constituting part, extracts an the-other-image object region that includes an image similar to the one-image object region from the other image by using the background degree, and thereby calculates the parallax between the one-image object region and the the-other-image object region.